The long-term goal of our investigations is to understand the functional role of certain neuronal subtypes in the processing of sound in the cortex. Understanding this circuitry is likely to have an impact on the diagnosis and treatment of clinically important cortical neuropathologies, including autism, schizophrenia, tinnitus and epilepsy. Our central hypothesis is that a certain subtype of inhibitory neuron plays an important role in determining how other cortical neurons respond to sound. To achieve our goals, we propose to monitor and perturb the activity of these neurons. In aim 1, we will study this circuit in vitro, substituting electrical for auditory stimulation. In aims 2 and 3 we will study this circuit in vivo, presenting simple sounds and monitoring the responses they elicit in single neurons, and looking at their role in an auditory behavior. If successful, our studies will provide the link between molecular, circuit and functional aspects of sound processing in the auditory system, and will facilitate the development of treatments for psychiatric and neurological diseases. This proposal will test the function of a particular class of cortical neurons implicated in the etiology of clinically important neuropathologies, including autism, schizophrenia, tinnitus and epilepsy. If successful, our studies will lead to improved strategies for diagnosing and treating these and related disorders.